To prevent leakage of body exudates from absorbent articles such as feminine care pads or napkins and disposable diapers, it is desirable that the exudates not reach the edges of the absorbent material in the article. A xe2x80x9ccenter fillxe2x80x9d strategy is desirable for leakage control, wherein fluids are preferentially held in a central region of the article. Further, absorbent articles with center fill strategies are desirable for the clean appearance they offer and the reduced wetted area in contact with skin. Unfortunately, in traditional absorbent articles, there is generally no barrier to bulk flow or capillary wicking from the target region to the edges of the article.
Efforts to prevent leakage from the sides of absorbent articles include using fluid impervious cuffs and flaps. These added barriers are costly and do not prevent fluid from reaching the edge of the absorbent article, though they can be effective in reducing leakage in some absorbent articles.
Central meltblown strips and other narrow strips of absorbent material have been added to the body side of absorbent articles to promote center filling of the articles. However, meltblown strips interfere with absorption of fluid into the absorbent cellulosic portions of the article and can hold wet fluid near the skin. Other efforts at controlling fluid intake to promote central filling have used narrow strips of cellulosic or other absorbent material with a horizontal barrier between the strip and the underlying absorbent core. The horizontal barrier material for delaying wicking provides vertical isolation of the central strip from the absorbent core, but does not prevent flow out of the sides of the wetted strip or toward the sides of the article. Further, the horizontal fluid barrier often occupies a significant portion of the article""s surface area and can result in ineffective use of the underlying absorbent core.
Embossing has also been used to promote longitudinal fluid flow, but embossments generally are not successful in preventing lateral wicking and in promoting true center fill. Furthermore, heavy embossing can be an ineffective use of absorbent material since the embossed regions are typically highly densified, generally having little pore volume for absorption of fluid.
Longitudinal chambers have also been used wherein each channel or chamber of absorbent material is completely isolated from the next by means of impervious or flow restricting walls. In some cases, however, isolated chambers represent a poor use of absorbent material as one chamber may become overloaded and overflow onto the cover, resulting in smearing and inefficient use of the absorbent material in other chambers. Successful use of isolated chambers requires improvements for prevention of chamber overflow, prevention of undesirable surface transport and smearing, and improved use of the absorbent material in the absorbent article. Further, prior attempts at isolated flow chambers are generally complex in execution, costly, and may suffer from poor product integrity. Improved approaches are needed that can be mass produced for low cost while achieving high levels of performance.
In general, what is needed is an improved means for promoting center fill and reducing flow toward the edges of the absorbent article for leakage reduction that offers improved feel and appearance of the article while also reducing smearing or other forms of failure.
In one aspect, the present invention resides in an absorbent article having a longitudinal direction, a transverse direction, a vertical direction substantially normal to both the longitudinal and transverse directions, and a body side, the absorbent article comprising:
a) an absorbent core having a body side surface, the core comprising an outer absorbent member having a central void open toward the body side of the absorbent article, and a central absorbent member disposed over the central void of the outer absorbent member and extending into the void; and
b) a wicking barrier disposed between the outer absorbent member and the central absorbent member, the wicking barrier comprising a vertical component and a horizontal component, the vertical component spanning a vertical distance between the outer absorbent member and the central absorbent member, and the horizontal component spanning a horizontal distance on the body side surface of the absorbent core.
In another aspect, the invention resides in an absorbent article having a body side, the absorbent article comprising an absorbent core having a body-side surface and comprising an outer absorbent member and a central absorbent member having a perimeter, and a wicking barrier spanning a vertical distance disposed along at least a portion of the perimeter of the central absorbent member, the wicking barrier also comprising a horizontal component residing on the body-side surface of the absorbent core.
In another aspect, the invention resides in an absorbent article having a longitudinal direction, a transverse direction, and a vertical direction substantially normal to both the longitudinal and transverse directions, a crotch region, and a body side, the absorbent article comprising:
a) an absorbent core having a body side surface, the absorbent core comprising a central absorbent member surrounded by a outer shaping member with a central void for receiving the central absorbent member;
b) a baffle layer beneath the central absorbent member; and
c) a wicking barrier disposed between the outer shaping member and the central absorbent member, the wicking barrier comprising a vertical component and a horizontal component, and the horizontal component spanning a horizontal distance on the body side surface of the outer shaping member.
In another aspect, the invention resides in an absorbent article with a longitudinal direction, a transverse direction, a vertical direction substantially normal to both the longitudinal and transverse directions, a body side, and a garment side, the absorbent article comprising:
a) an absorbent core having a central absorbent member and an outer absorbent member, the outer absorbent member having a central void defined therein for receiving at least a portion of the central absorbent member, whereby an interface is defined between the central absorbent member and the outer absorbent member; and
b) a wicking barrier, desirably a single-ply wicking barrier, disposed along the interface between the central absorbent member and the outer absorbent member, the wicking barrier spanning a vertical distance in the absorbent article and having a variable liquid permeability such that the liquid permeability of the wicking barrier is lower near the body side and higher near the garment side.
The wicking barrier can extend downward from the surface of the absorbent core to span a vertical distance less than the vertical distance of the interface, or, alternatively, can extend substantially along the entire vertical distance of the interface and is provided with apertures or openings away from the body side of the absorbent core such that fluid passing through the wicking barrier must follow an elongated or tortuous path to pass out of the central absorbent member. The wicking barrier can also be provided with a horizontal component on or near the surface of the absorbent core spanning a horizontal distance to reduce the likelihood of contact between the outer absorbent member and the central absorbent member when the article is laterally compressed or bunched together in use.
In another aspect, the invention resides in an absorbent article with a crotch region, a longitudinal direction, a transverse direction, and a vertical direction substantially normal to both the longitudinal and transverse directions, the absorbent article comprising:
a) an absorbent core having a central absorbent member and an outer shaping member, the outer shaping member having a central void defined therein for receiving at least a portion of the central absorbent member, whereby an interface is defined between the central absorbent member and the outer shaping member, the interface spanning a vertical distance, the outer shaping member suitably having a thickness of at least about 1 mm, an edge width of at least about 2 mm, and a basis weight of at least about 100 gsm; and
b) a wicking barrier disposed along the interface between the central absorbent member and the outer absorbent member.
In another aspect, the invention resides in an absorbent article comprising an absorbent core comprising an outer absorbent member and a central absorbent member, the outer absorbent member having a central void therein for receiving an insert, and the central absorbent member being inserted into the central void, and a wicking barrier between the outer absorbent member and the central absorbent member, the wicking barrier spanning a vertical distance that can be substantially as great as the thickness of the central absorbent member or can be less than the thickness of the central absorbent member. The central void can be a hole that passes completely through the outer absorbent member, or can be a depressed region within a contiguous, uninterrupted outer absorbent member. Desirably, the wicking barrier comprises a horizontal component that serves as a ledge on the surface of the absorbent core. In one embodiment, the central void longitudinally divides the outer absorbent member into two noncontiguous sections. In other embodiments, the outer absorbent member is divided by the central void in the crotch region, but the outer absorbent member may be contiguous in the front or back portions of the article (i.e., the central void does not extend substantially beyond the crotch region).
In another aspect, the present invention resides in an absorbent article comprising a composite absorbent core having a center, the absorbent core having a body side surface and comprising a central absorbent member and a surrounding outer absorbent member, wherein a plurality of vertically oriented segments of hydrophobic material in the central absorbent member define liquid wicking pathways from the center of the central absorbent member to the outer absorbent member.
In another aspect, the invention resides in an absorbent article comprising a backsheet and a concentric absorbent structure attached to the backsheet, the concentric absorbent structure having a thickness and comprising multiple alternating concentric layers of barrier material and absorbent material, wherein the barrier material substantially spans the thickness of the concentric absorbent structure.
In another aspect, the invention resides in a method for producing an absorbent article having a central absorbent member, the method comprising:
a) preparing an outer absorbent member, wherein the outer absorbent member has a central void;
b) deposing a layer of a flexible barrier material over the central void; and
c) inserting a section of absorbent material into the central void and over the barrier material to form a central absorbent member, such that a portion of the barrier material separates the central absorbent member from the outer absorbent member along a vertical distance.
The above method may further comprise deposing a backsheet beneath the absorbent core; deposing a topsheet above the absorbent core; and attaching a portion of the topsheet to a portion of the backsheet.
In another aspect, the invention resides in a method for producing an absorbent article having a central absorbent member, a garment side, and a body side, the method comprising:
a) preparing an outer shaping member having a first portion and a second portion with a central void between the first portion and the second portion, wherein the central void has a vertical depth and the outer shaping member has a surface comprising a wicking barrier that spans at least a portion of the vertical depth of the central void; and
b) inserting an absorbent material into the central void of the outer shaping member to form a central absorbent member.
In yet another aspect, the invention resides in a method of preparing an absorbent article comprising a concentric absorbent structure with multiple vertical wicking barriers interposed between layers of absorbent material, the method comprising:
a) superposing at least one layer of a barrier material onto at least one layer of absorbent material to form a multilayered structure;
b) rolling the multilayered structure about a rolling axis to form a spiral wound roll;
c) slicing a portion of the spiral wound roll substantially normal to the rolling axis to form a substantially concentric absorbent structure; and
d) attaching the substantially concentric absorbent structure to a backsheet.